geocoding location from input box


I'm new to google maps and simply trying to get the hang of it. I want to be able to type in a city or address, and then have the map load it and place a marker.

Right now my map loads fine initially, but when I type in a city or address nothing happens. Any idea what's going on here?

<script type="text/javascript">
var geocoder;
var map;
  function initialize() {
    geocoder = new google.maps.Geocoder();
    var latlang = new google.maps.LatLng(42, -84);
    var myOptions = {
        center: latlang, zoom: 5, mapTypeId: google.maps.MapTypeId.SATELLITE,
        navigationControlOptions: {
            style: google.maps.NavigationControlStyle.SMALL
        }
    };
    var map = new google.maps.Map(document.getElementById("map_canvas"),
        myOptions);
  }

  function codeAddress() { 
    var sAddress = document.getElementById("newLocation").value;
    geocoder.geocode( { 'address': sAddress}, function(results, status) { 
            if (status == google.maps.GeocoderStatus.OK) {
                map.setCenter(results[0].geometry.location);
                var marker = new google.maps.Marker({
                map: map,
                position: results[0].geometry.location
                });
            }
            else{
            alert("Geocode was not successful for the following reason: " + status);
            }
        });
  }
</script>
</head>
  <body onload="initialize()">
    Address: <input type="text" id="newLocation" style=" width:200px" title="Address to Geocode" />     
    <input type="button" onclick="codeAddress()" id="inputButtonGeocode" style="width:150px" title="Click to Geocode" value="Geocode" />
    <div id="map_canvas" style="width:100%; height:100%"></div>
  </body>
</html>

In the line

var map = new google.maps.Map(document.getElementById("map_canvas")...

remove the word var. Because it creates map in a functionally local scope and the geocoding function only sees the prior (empty) map variable. By removing it the global map variable is updated to this new google map.